Bonus section cog for wall next to waterfall and handles for the circular entrance in front of wate

I cannot zoom in on the wall with cog wheels. I have a cog wheel., tweezers , lighter and a knife. The circular lid in front of waterfall says I need handles. The hints say try another location. I cannot work out what I have to do. Have I missed picking up an object or is it a glitch in the game. Any help would be most welcome.